From the photographer: "Every sunrise and sunset, provided there are no clouds, Mauna Kea casts its shadow on the Earth's atmosphere, creating a distinctive triangular shaped shadow. On rare occasions, the rising or setting Full Moon can be seen inside the shadow. In this photo, taken two weeks before the 1991 total solar eclipse, the Moon had just emerged from a penumbral lunar eclipse. The sunlight that is illuminating the Moon is passing around the other side of the Earth."
Richard Wainscoat - http://www.wainscoat.com/